Thinking in Systems: A Primer

by Donella H. Meadows

The behavior of a system cannot be known just by knowing the elements of which the system is made.

A system* is an interconnected set of elements that is coherently organized in a way that achieves something. If you look at that definition closely for a minute, you can see that a system must consist of three kinds of things: elements, interconnections, and a function or purpose.

is because of fractal geometry that the average human lung has enough surface area to cover a tennis court.)

central rules and regulations prevent students or faculty from exploring fields of knowledge freely, the purpose of the university is not served.

Resilience, self-organization, and hierarchy are three of the reasons dynamic systems can work so well. Promoting or managing for these properties of a system can improve its ability to function well over the long term—to be sustainable.

Tree ring records show that the spruce budworm has been killing spruce and fir trees periodically in North America for at least 400 years. Until this century, no one much cared. The valuable tree for the lumber industry was the white pine. Spruce and fir were considered “weed species.” Eventually, however, the stands of virgin pine were gone, and the lumber industry turned to spruce and fir. Suddenly the budworm was seen as a serious pest. So, beginning in the 1950s, northern forests were sprayed with DDT to control the spruce budworm. In spite of the spraying, every year there was a budworm resurgence. Annual sprays were continued through the 1950s, 1960s, and 1970s, until DDT was banned. Then the sprays were changed to fenitrothion, acephate, Sevin, and methoxychlor. Insecticides were no longer thought to be the ultimate answer to the budworm problem, but they were still seen as essential. “Insecticides buy time,” said one forester, “That’s all the forest manager wants; to preserve the trees until the mill is ready for them.” By 1980, spraying costs were getting unmanageable—the Canadian province of New Brunswick spent $12.5 million on budworm “control” that year. Concerned citizens were objecting to the drenching of the landscape with poisons. And, in spite of the sprays, the budworm was still killing as many as 20 million hectares (50 million acres) of trees per year. C. S. Holling of the University of British Columbia and Gordon Baskerville of the University of New Br...

There are only boundaries of word, thought, perception, and social agreement—artificial, mental-model boundaries.

Disorderly, mixed-up borders are sources of diversity and creativity.

boundaries are of our own making, and that they can and should be reconsidered for each new discussion, problem, or purpose.

There always will be limits to growth. They can be self-imposed. If they aren’t, they will be system-imposed.

We are not omniscient, rational optimizers, says Simon. Rather, we are blundering “satisficers,” attempting to meet (satisfy) our needs well enough (sufficiently) before moving on to the next decision.

bounded rationality

The bounded rationality of each actor in a system—determined by the information, incentives, disincentives, goals, stresses, and constraints impinging on that actor—may or may not lead to decisions that further the welfare of the system as a whole.

This option, helping the system to help itself, can be much cheaper and easier than taking over and running the system—something liberal politicians don’t seem to understand. The secret is to begin not with a heroic takeover, but with a series of questions.

Why are the natural correction mechanisms failing? How can obstacles to their success be removed? How can mechanisms for their success be made more effective?

It measures effort rather than achievement, gross production and consumption rather than efficiency.

In fact, we don’t talk about what we see; we see only what we can talk about.

Native American cultures actively spoke of and considered in their decisions the effects on the seventh generation to come. The longer the operant time horizon, the better the chances for survival.